1. Field of the invention:
The present invention relates to an air conditioner for a vehicle provided with a cooler cooled in a cooling circuit which includes a compressor, and control method therefor. More particularly, it relates to an air conditioner for a vehicle adapted to air-cool the interior of a car by additional capability of the cooler when the temperature inside the car room is above a set value, and a control method therefor.
2. Description of the Prior Art:
There is generally provided an air conditioner for a vehicle such as a car to keep the temperature inside the car comfortable.
A prior air conditioner for a vehicle is provided with a cooler air-cooled in a cooling circuit which includes a compressor, and adapted to supply air cooled by the cooler into the vehicle interior. Power for the compressor is provided from the vehicle engine via a magnetic clutch which is turned on and off by an output signal issued from a temperature sensor provided for measuring the temperature of the cooler.
In the prior vehicle air conditioner for vehicle thus constructed, the temperature of the cooler is measured by the temperature sensor which in turn causes the magnetic clutch to be turned on when the measured temperature is over a set temperature to thereby the compressor to be driven for supplying cooling air into the car. Thereafter, when the measured temperature becomes less than the set temperature, the magnetic clutch is turned off, and thereby operation of the compressor is stopped.
Hereupon, particularly in midsummer, temperature in a car interior is initially lowered to a temperature less than the set one by operation of the compressor, but provided that the operation of the compressor is stopped, the temperature in the car room is immediately raised due the temperature outside the car, causing successive operation of the compressor to be readily effected. Consequently, the compressor repeatedly starts and stops at frequent intervals. In addition, a load is imposed on the engine due the operation of the compressor. The compressor must be accordingly stopped when necessitated by engine operating conditions. This results in the drawback that is impossible to cool the interior of the car during the stoppage of the compressor.
There has been in Japanese Laid-Open Patent Publication No. 57-1445 an approach to resolve such a problem of of a prior air conditioner for vehicle. The apparatus according to this disclosure serves to stop a compressor, and reduce the load on the engine, when the number of engine revolutions is less than a prescribed value while cooling the interior of the car. Namely, the apparatus stores cooling heat from a cooler in a brine solution and then radiates the stored heat when the number of engine revolutions becomes less than a prescribed value.
However, the above-described apparatus suffers from as a drawback that the cooling heat from the cooler is not effectively transferred into the brine solution and thus is not stored therein. In addition, it has as a drawback that radiation of the stored cooling heat is dependent only on the number of engine revolutions, and is independent of the temperature in the car interior. Accordingly, there may be a case according to circumstances in which the above-described cooling heat is further radiated although the temperature in the car interior has been lowered to a set value, and thus the interior of the car is excessively cooled.